 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.update.internal.core;

 import java.util.HashMap ;
 import java.util.Map ;

 import org.eclipse.core.runtime.*;
 import org.eclipse.osgi.util.NLS;
 import org.eclipse.update.core.*;

 /**
  * Manages FeatureFactory extension point
  */
 public final class FeatureTypeFactory {

     private static FeatureTypeFactory inst;
     private Map factories;

     private static final String SIMPLE_EXTENSION_ID = "featureTypes"; //$NON-NLS-1$

     /*
      * hide constructor
      */
     private FeatureTypeFactory() {
     }

     /*
      * Singleton pattern
      */
     public static FeatureTypeFactory getInstance() {
         if (inst == null)
             inst = new FeatureTypeFactory();
         return inst;
     }

     /*
      * return the factory for the associated type
      */
     public IFeatureFactory getFactory(String type) throws CoreException {
         //
 Object instance = getFactories().get(type);
         if (instance == null) {
             instance = createFactoryFor(type);
             getFactories().put(type, instance);
         }
         return (IFeatureFactory) instance;
     }

     /*
      * creates a factory for the associated type and cache it
      */
     private IFeatureFactory createFactoryFor(String type) throws CoreException {
         IFeatureFactory result = null;

         String pluginID =
             UpdateCore.getPlugin().getBundle().getSymbolicName();
         IExtensionRegistry registry = Platform.getExtensionRegistry();
         IConfigurationElement[] elements =
             registry.getConfigurationElementsFor(pluginID, SIMPLE_EXTENSION_ID, type);

         if (elements == null || elements.length == 0) {
             throw Utilities.newCoreException(
                     NLS.bind(Messages.FeatureTypeFactory_UnableToFindFeatureFactory, (new String [] { type })),
                     null);
         }

         IConfigurationElement element = elements[0];
         result = (IFeatureFactory) element.createExecutableExtension("class"); //$NON-NLS-1$
 return result;
     }

     /*
      *
      */
     private Map getFactories() {
         if (factories == null)
             factories = new HashMap ();
         return factories;
     }
 }

